The present invention relates to tuners, and has particular applicability to television receiver tuners, although the present invention will be applicable to tuners for other types of devices.
It is typical in the television industry today to form a tuner having a set of serially arranged varactor tuned circuits or "tanks" receiving a signal from the television antenna. The tuned circuits provide an output which is highly selective in frequency so as to minimize cross modulation and other undesired signals when the circuits are properly tuned. This set of varactor tuned circuits has heretofore been ganged so that a single input voltage controls every varactor tuned circuit. Generally this set of tuned circuits is aligned in a factory operation wherein a technician will input a frequency corresponding to a low television channel to the set and adjust each tuned circuit for maximum response at that one frequency. Then further alignment is done for a higher frequency channel and an intermediate frequency channel. The alignment compensates for the tolerances in the components forming each tuned circuit. After the alignment, the three channels will be properly aligned. However, often there will be some mistracking on other channels which have not been aligned.
It is an object of the present invention to provide a tuner which overcomes this mistracking on other channels.
Another object of the present invention is to provide a tuner which aligns itself automatically and therefore requires minimal or no factory adjustment.
Another object of the invention is to provide a method for automatically and electronically adjusting the set of tunable circuits in a television tuner.